DESCRIPTION (Scanned from the Applicant's Description): Lipoprotein lipase (LPL) is a central enzyme in lipid metabolism and adipocyte biology. Although the changes in LPL activity with diabetes and other conditions have been well described, the mechanism of LPL regulation is complex. We have described regulation of LPL translation in response to catecholamines, thyroid hormone, and in diabetes. Our recent studies have described an RNA binding protein that inhibited translation through binding to the 3'UTR of the LPL mRNA. We have now identified a member of the RNA binding complex as the alpha catalytic subunit of cAMP dependent protein kinase (PKA). In addition, we have produced transgenic mice that express an LPL gene (LPLt) that lacks the RNA binding motif on the 3'UTR. Our future aims are to better characterize the role of PKA in LPL regulation, and to better understand the role of translation in the physiologic regulation of LPL. Hypothesis 1. Protein kinase A (PKA) is involved in the translational regulation of LPL. Aim 1. Characterize the binding of the PKA C subunit to LPL mRNA: tissue specificity and involvement of other proteins. Aim 2. Determine the sequence and kinase activity of the C subunit involved in translational regulation. Aim 3. Characterize the motif on the 3'UTR of LPL that is involved in C binding. Aim 4. Determine whether LPL translation is altered in PKA knockout mice. Hypothesis 2. Regulation of LPL translation is important physiologically. Aim 1. Examine the translational regulation of both LPLt and wild type LPL (LPLwt) in response to epinephrine, thyroid hormone, and phorbol ester in isolated adipocytes from transgenic mice. Aim 2. Examine the regulation of LPLt and LPLwt in adipose tissue of transgenic mice following the induction of streptozotocin-diabetes or hypothyroidism, and the in vivo administration of epinephrine. Aim 3. Examine the mechanism by which the expression of LPLt in transgenic mice is accompanied by a down regulation of wild type LPL.